A servomotor velocity control system according to the present invention control velocity by using an observer for obtaining a sensed value of velocity while estimating motor load torque. When resolution of a rotary encoder is a problem in a region of low motor velocities, this is compensated for to improve the velocity sensing precision in the low-velocity region. In a region of high motor velocities, velocity processing is executed based on the output of the rotary encoder considering the processing time of a CPU. Use or non-use of the observer for obtaining the estimated value of velocity is selected in dependence upon the velocity of the motor.